Hi there! Beam Debugging Noob here.
I have a Hetzner Cloud VPS server (1 vCPU, 2GB RAM) with Ubuntu 18.04.2 and dokku installed. There’s an Elixir Phoenix application running in a docker container, running on Erlang 20.1 and Elixir 1.7.4, not the latest but I got errors trying to deploy newer versions. The machine experiences almost no load and reports having more than 1GB of RAM available.
Sometimes, after the container has been running for a while, the beam.smp process in the docker container will segfault, like it has done in the past few days:
Jun 16 19:48:40 nepasheli-1 kernel: [16533055.262703] 1_scheduler: segfault at 208 ip 0000000000608ce4 sp 00007f135077e940 error 4 in beam.smp[400000+339000] ... Jun 19 12:58:56 nepasheli-1 kernel: [58674.014500] 1_scheduler: segfault at 208 ip 0000000000608ce4 sp 00007fcbc50be8e0 error 4 in beam.smp[400000+339000]
The first segfault at Jun 16 went unnoticed by me, apparently some dokku magic redeployed the container.? But after todays segfault at Jun 19 it was still down when I noticed it about 20 minutes later. I had to redeploy the container to get things running again.
Does anyone recognize such behavior? Is error 4 in beam.smp a well known error? How to debug such crashes inside a docker container? Googling ‘beam.smp error 4’ did not return really good results. All help, pointers and insights are welcome.